ESTCP Project #1011, Rhizosphere
Final Report
1.2 Objectives of the Demonstration
The objective of rhizosphere-enhanced remediation was to treat POL-contaminated soils in
northern regions where low temperatures, site inaccessibility, and freeze-thaw cycles limit or
prevent cost-effective application of either traditional technologies or emerging innovative
technologies. In this study, we demonstrated and validated the ability of cold-tolerant plants,
nutrient additions, and their combination to remediate POL-contaminated soils in cold regions.
Data from the field demonstration sites have been evaluated to determine the effect of these
factors on soil concentrations of POLs at three geographically diverse sites in Alaska: Annette
Island (southern), Galena-Campion (interior), and Barrow (North Slope). We documented
seeding, monitoring, and site-specific conditions for each location under which the technology
was applied. We evaluated the technology in terms of its overall cost, regulatory acceptance, and
the practicality of implementation.
1.3 Regulatory Drivers
This project addressed cleanup and restoration of contaminated soils resulting from DoD
activities on Native American lands. It also addressed cleanup requirements developed by user
groups within DoD for (1.3.b) On-Site Treatment of Organics Contaminated Soils and (1.3.m)
Soil Bioremediation. Native American Communities and a Native American owned small
businesses, ClearWater Environmental Services, Incorporated, were partners in the
demonstrations at the Annette Island and Campion sites. At Annette Island, we coordinated
closely with the Metlakatla Indian Community, and they were active partners in site selection.
We sought assistance from Ilisagvik College in Barrow, Alaska, but were unable to develop an
active partnership.
The state regulations that apply to this technology are those for petroleum-contaminated soils.
These regulations generally address sampling frequency and protocols, but were developed to
address more aggressive remediation technologies where treatments effects are more readily
measured. Regulations for low-cost remediation strategies are still evolving in Alaska as well as
many locations in the US.
1.4 Stakeholder / End-User Issues
An important issue for users is scientifically defensible data showing that rhizosphere-enhanced
treatment provides a benefit relative to natural attenuation. Lack of these data has limited
acceptance of rhizosphere-enhanced remediation. These data are useful in showing that
rhizosphere-enhanced remediation has a measurable and significant impact on treating
petroleum-contaminated surface soils using low-cost methods that require minimal maintenance
and can be used over large areas. Importantly, they also demonstrate that commonly employed
monitoring methods will be insufficient for detecting changes in the contaminant concentrations
in surface soils undergoing plant-based treatment. The benefits of these findings are that this
plant-based approach does have a positive effect for treating surface soils, and that monitoring
methods will need to be adjusted to successfully observe these changes.
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